There is now significant evidence for the secretion of transformed cell-specific factors to culture medium and in vivo. The purpose of the present investigation is to confirm the identity of the factors released from specific tumor cells in vivo to curculation and in vitro to culture medium by physico-chemical, biochemical and immunochemical techniques. Subsequently, the development of an RIA will permit a study of their accumulation and clearance from circulation. By use of standard immunochemical and physico-cehmical techniques, we shall evaluate the similarity of these phospoprotein factors with respect to the inducing carcinogen, the target organ and the animal species. With reference to the long term objective these basic studies will determine the feasibility of using the factors as a basis for a general test for the hpresence in the animal of transformed (tumor) cells. If validated as a general test, it would be a very useful test to both clinicians and to regulatory agencies.